This invention relates generally to the area of a signalling protocol received by a portable selective call receiver, such as a paging receiver, and a method of receiving the signal.
Paging protocols have been designed to communicate messages to a number of pagers. A message consists of an address signal if the message is a tone only message, or an address signal and an information signal if the message is a data message. Typically, a multiplicity of messages are accumulated prior to transmitting a selective call signal having the multiplicity of messages. Certain advantages exist in grouping the address signals of the multiplicity of messages into an address field and grouping the information signals of the multiplicity of messages into a data field transmitted subsequent to the address field.
Such a selective call signal is shown in U.S. Pat. No. 4,668,949, issued May 26, 1987, to Akahori et al. entitled "Pager Receiver Comprising a Message Detector Energized Only at Pertinent Time Slots". In this patent, the first data packet in the data field was associated with the first address slot in the address field, and subsequent data packets were associated with subsequent address slots.
Although this patent discloses some advantages of separate address and data fields, the invention has several disadvantages when adapted for use with conventional paging messaging applications. First, no provision is made for efficient tone only messaging. A tone only message would result in an unused data packet in the data field. Additionally, no provision is made for a variable number of address slots. The address field contains exactly eight address slots for address signals, no more or no less slots, each address slot having exactly one data packet associated therewith. Furthermore, no provision is made for data messages larger than the predetermined amount of information within a single packet. Thus, data messages are restricted to be smaller than a predetermined size. It is desirable to provide a remedy for these disadvantages while providing for separate address and data fields in a selective call signalling protocol.
Furthermore, the prior art provided for only a single class of battery saving pagers. No provision was made for pagers which may require a high performance battery saving algorithm.